The PDP industry has used two different AC plasma display panel (PDP) structures, the two-electrode columnar discharge structure and the three-electrode surface discharge structure. The two-electrode columnar discharge display structure is disclosed in U.S. Pat. No. 3,499,167 issued to Baker et al. and U.S. Pat. No. 3,559,190 issued to Bitzer et al. The two-electrode columnar discharge structure is also referred to as opposing electrode discharge, twin substrate discharge, or co-planar discharge. In the two-electrode columnar discharge AC plasma display structure, the sustaining voltage is continuously applied between an electrode on a rear or bottom substrate and an opposite electrode on the front or top viewing substrate. The gas discharge takes place between the two opposing electrodes in between the top viewing substrate and the bottom substrate.
The columnar discharge structure has been widely used in monochrome AC plasma displays that emit orange or red light from a neon gas discharge. Typically phosphors are not used in such monochrome structures.
The present invention relates to a surface discharge AC plasma display panel having a structure with three or more electrodes defining each pixel or cell. In a three-electrode surface discharge AC plasma display, a sustaining voltage is applied between a pair of adjacent parallel electrodes that are on the front or top viewing substrate. These parallel electrodes are called the bulk sustain electrode and the row scan electrode. The row scan electrode is also called a row sustain electrode because of its dual functions of address and sustain. The opposing electrode on the rear or bottom substrate is a column data electrode and is used to periodically address a row scan electrode on the top substrate. The sustaining voltage is applied to the bulk sustain and row scan electrodes on the top substrate. The gas discharge takes place between the row scan and bulk sustain electrodes on the top viewing substrate.
As disclosed and illustrated in Baker ('167), the two-electrode columnar discharge AC plasma display panel is an opposite discharge display with the sustaining voltage being applied to the two opposite top and bottom electrodes. The discharge takes place between these two opposing electrodes and in between the opposing top and bottom substrates. In a multi-color columnar discharge (PDP) structure as disclosed in U.S. Pat. No. 5,793,158 issued to Donald K. Wedding, phosphor stripes or layers are deposited along the barrier walls on the bottom substrate adjacent to and extending in the same direction as the bottom electrode. The discharge between the two opposite electrodes generates electrons and ions that bombard and deteriorate the phosphor thereby shortening the life of the phosphor and the PDP.
In contrast, in a three-electrode surface discharge AC plasma display panel, the sustaining voltage and resulting gas discharge occurs between the electrode pairs on the top or front viewing substrate above and remote from the phosphor on the bottom substrate. This separation of the discharge from the phosphor prevents electron bombardment and deterioration of the phosphor deposited on the walls of the barriers or in the grooves (or channels) on the bottom substrate adjacent to and/or over the third (data) electrode. Because the phosphor is spaced from the discharge between the two electrodes on the top substrate, the phosphor is not subject to electron bombardment as in a columnar discharge PDP.
In a surface discharge PDP, each light emitting pixel or cell is defined by the gas discharge between two electrodes on the top substrate. In a multi-color RGB display, the pixels may be called sub-pixels or sub-cells. Photons from the discharge of an ionizable gas at each pixel or sub-pixel excite a photoluminescent phosphor that emits red, blue, or green light.
In a two electrode columnar discharge PDP as disclosed by Wedding ('158), each light emitting pixel is defined by a gas discharge between a bottom or rear electrode x and a top or front opposite electrode y, each cross-over of the two opposing arrays of bottom electrodes x and top electrodes y defining a pixel or cell.
The three-electrode multi-color surface discharge AC plasma panel structure is widely disclosed in the prior art including U.S. Pat. Nos. 5,661,500 (Shinoda et al.), 5,674,553, (Shinoda et al.), 5,745,086 (Weber), and 5,736,815 (Amemiya), all of which are incorporated herein by reference.
For reasons discussed above and also as presented in TABLE I hereafter, the multi-color columnar discharge PDP with phosphors has not been successfully commercialized in the PDP industry. However, the multi-color surface discharge PDP has been successfully commercialized and is presently been widely manufactured by a number of firms.
TABLE I presents a comparison and overview of the two-electrode multi-color columnar discharge PDP structure versus the three-electrode multi-color surface discharge PDP structure at a sustain frequency of 30 kHz and a gas mixture containing less than 6% xenon.
TABLE IAC PLASMA DISPLAY STRUCTURESCOLUMNAR DISCHARGE vs SURFACE DISCHARGEAttributeColumnar DischargeSurface DischargeNumber of Electrodes23Phosphor DepositionUnforgiving: PhosphorForgiving: Phosphorcannot cover electrodeentirely covers theat discharge sites onelectrode on thethe bottom substrate.bottom substrate.Will decrease life ofWill not decrease lifephosphor and panelof phosphor and panelNumber of Bits per Color@ 640 × 480 resolution8 bits8 bits@ 1280 × 1240 pixels6 bits8 bitsDisplay Colors @262,14416,777,2161280 × 024 pixelsLuminance FL @<20>6030 KHz sustainPower, Watts @30 KHz sustain19-21″ diagonal150-200 W110 W640 × 480 pixels19-21″ diagonal   200 W1280 × 1024 pixels25″ diagonal   220 W200 W1280 × 1024 pixels30″ diagonal350-400 W1024 × 768 pixels42″ diagonal350 W856 × 480 pixelsLuminous Efficiency,0.05 to 0.41.0 to 1.5Lumens per Watt,at 30 KHz sustainOperating Life in<2000>10,000Hours @ 30 KHzsustain and 20%fill factorContrast Ratio<20:1>100:1Peak Discharge4 times Surface PeakCurrentDischargeEMIMuch higher becauseof high peak dischargecurrent
As summarized in TABLE I, the three-electrode surface discharge PDP superiority over the two-electrode columnar discharge PDP includes lower power, longer life, greater contrast, lower peak discharge current, higher luminance (brightness), and higher luminous efficiency. The high peak discharge current of columnar discharge greatly adds to the costs of the electronic circuitry.
Surface discharge also has manufacturing advantages over columnar discharge. One of these (phosphor deposition) is listed in TABLE I. The deposition of phosphor in the manufacture of surface discharge is very forgiving because the phosphor covers the electrodes on the back (bottom) substrate without decreasing panel life.
In a columnar discharge structure, the phosphor must be precisely deposited and cannot cover electrode discharge sites on the back substrate without further decreasing phosphor life. There is little or no forgiveness in deposition of the phosphor. It may also be necessary to use an overcoat such as magnesium oxide to protect the phosphor from discharge ion bombardment. However, a protective overcoat decreases light output from the phosphor. A protective phosphor overcoat is not used or required in the manufacture of a surface discharge display structure.
The surface discharge PDP structure is also much less sensitive than columnar discharge to variations in the gas discharge gap between the back and front substrates. In a columnar discharge PDP structure, the gap must be precisely controlled to avoid variations and distortions in luminance and chromaticity.